package day35_42.day35;

import java.util.Scanner;

public class Main01 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        while (sc.hasNext()) {
            int n = sc.nextInt();
            double ret = count(n)/fac(n);
            System.out.printf("%.2f", 100 * ret);
            System.out.println("%");
        }
    }

    public static double count(int n) {
        if(n==1){
            return 0;
        }
        if(n==2) {
            return 1;
        }
        return (n-1)*(count(n-1)+count(n-2));
    }
    public static double fac(int n){
        if(n==0){
            return 1;
        }else{
            return n*fac(n-1);
        }
    }
}

